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Abstract:

A vehicle lamp includes a plurality of light sources, and a light guide
plate configured to emit light to the front side of the lamp from a
second surface facing a first surface by internally reflecting light,
which is emitted from the respective light sources, by a plurality of
reflective elements formed on the first surface after causing the light
to enter the light guide plate from a rear end face of the light guide
plate. The light guide plate is curved to the first surface and gradually
becomes thinner toward the front side. The reflective elements are
disposed at a predetermined interval in a longitudinal direction and
extend in a direction crossing the longitudinal direction.

Claims:

1. A vehicle lamp comprising: a plurality of light sources; and a light
guide plate arranged to emit light to the front side of the lamp from a
second surface facing a first surface by internally reflecting light,
which is emitted from the respective light sources, by a plurality of
reflective elements on the first surface after causing the light to enter
the light guide plate from a rear end face of the light guide plate,
wherein the light guide plate is curved to the first surface and
gradually becomes thinner toward the front side, and the plurality of
reflective elements are disposed at a predetermined interval in a
longitudinal direction and extend in a direction crossing the
longitudinal direction.

2. The vehicle lamp according to claim 1, wherein a longitudinal width of
the reflective element, which is positioned on the further front side, of
the respective reflective elements is set to a larger value.

3. The vehicle lamp according to claim 1, wherein the light guide plate
is curved to the second surface toward an end portion in a direction
orthogonal to the longitudinal direction.

4. The vehicle lamp according to claim 2, wherein the light guide plate
is curved to the second surface toward an end portion in a direction
orthogonal to the longitudinal direction.

Description:

CROSS-REFERENCE TO RELATED APPLICATION(S)

[0001] The present application claims the benefit of priority of Japanese
Patent Application No. 2011-149152, filed on Jul. 5, 2011, the contents
of which are incorporated herein by reference.

BACKGROUND

[0002] 1. Technical Field

[0003] The present disclosure relates to a vehicle lamp including a light
guide plate.

[0004] 2. Related Art

[0005] Some vehicle lamps are adapted to emit light to the front side of
the lamp from its front surface by internally reflecting light, which is
emitted from a plurality of light sources such as light-emitting diodes,
by a plurality of reflective elements formed on its rear surface after
making the light enter a light guide plate from a rear end face thereof.

[0006] Japanese Patent Document JP-A-2005-122946, for example, discloses a
structure in which a side end face of the light guide plate, where the
light emitted from the respective light sources enters, is disposed close
to a rear end face in a direction facing the rear end face in such a
vehicle lamp.

[0007] If a structure that causes the light emitted from the respective
light sources to enter the light guide plate from the rear end face is
used as the structure of the light guide plate, it is possible to place
the light guide plate so that it is curved along the shape of the vehicle
body after easily securing a space in which the respective light sources
are disposed.

[0008] However, when the light emitted from the respective light sources
enters the light guide plate from the rear end face as described above,
it is necessary to cause the light to reach an emission surface of the
light guide plate at an incidence angle smaller than a critical angle in
order to emit the light, which enters the light guide plate, to the front
side of the lamp. This, however, is not necessarily easy. For this
reason, a problem can arise in that it also may not be easy to make the
light guide plate appear to emit light uniformly in the front view of the
lamp.

SUMMARY

[0009] One or more exemplary embodiments of the present invention provide
a vehicle lamp that can make a light guide plate appear to emit light
uniformly in the front view of the lamp even when the light guide plate
of the vehicle lamp has a structure that causes light emitted from
respective light sources to enter the light guide plate from a rear end
face.

[0010] In some implementations, the foregoing feature is achieved based on
a study on the shape of a light guide plate.

[0011] A vehicle lamp according to an exemplary embodiment includes a
plurality of light sources, and a light guide plate configured to emit
light to the front side of the lamp from a second surface facing a first
surface by internally reflecting light, which is emitted from the
respective light sources, by a plurality of reflective elements formed on
the first surface after making the light enter the light guide plate from
a rear end face of the light guide plate. The light guide plate is curved
to the first surface and gradually becomes thinner toward the front side.
The reflective elements are disposed at a predetermined interval in a
longitudinal direction and extend in a direction crossing the
longitudinal direction.

[0012] The type of the "light source" is not restricted and may be, for
example, a light-emitting diode.

[0013] As long as the "light guide plate" is curved to the first surface
and gradually becomes thinner toward the front side, the specific shape
of the light guide plate is not restricted. In this case, "curved to the
first surface toward the front side" means that the light guide plate is
curved so that a first surface side becomes concave and a second surface
side becomes convex in a longitudinal direction.

[0014] The "first surface side" may correspond to any one of an upward
direction, a downward direction, a left direction, a right direction, and
an inclined direction between the foregoing directions.

[0015] The "internal reflection" performed by the respective "reflective
elements" may be performed, for example, by total reflection and may be
performed as normal mirror reflection by performing mirror surface
treatment on the surfaces of the reflective elements.

[0016] In some implementations, it is possible to obtain the following
functional effect.

[0017] Light, which enters the light guide plate from the rear end face of
the light guide plate, is guided to the front side while total reflection
of the light is repeated sequentially by the first and second surfaces,
but the light guide plate is curved forward to the first surface.
Accordingly, at a position ahead of the rear end face of the light guide
plate to some extent, a portion of the light, which is reflected
internally by the reflective elements of the first surface, reaches the
second surface at an incidence angle smaller than a critical angle and is
emitted from the second surface to the front side of the lamp. Further, a
portion of the light, which continues to be guided further, is reflected
internally at a position further ahead of the position by the reflective
elements of the first surface, reaches the second surface at an incidence
angle smaller than a critical angle, and is emitted from the second
surface to the front side of the lamp.

[0018] In this case, since the light guide plate gradually becomes thinner
toward the front side, it is possible to obtain the following functional
effect.

[0019] If the thickness of the light guide plate, which is curved to the
first surface toward the front side, is constant, it is necessary to make
larger a level difference between the front or rear end edges of the
reflective elements, which are positioned on the further front side, of
the respective reflective elements in order to make the light, which is
reflected internally by the reflective elements 24s of the first surface,
reach the second surface at an incidence angle smaller than a critical
angle. However, the light, which is guided to the front end portion of
the light guide plate, decreases in this case. In that regard, if the
light guide plate gradually becomes thinner toward the front side, it is
possible to prevent a level difference between the respective reflective
elements from becoming excessively large and to guide light to the front
end portion of the light guide plate easily. Accordingly, it is possible
to make the light guide plate appear to emit light uniformly in the front
view of the lamp.

[0020] In some implementations, even when the guide plate of the vehicle
lamp including the light guide plate is adapted to cause light, which is
emitted from the respective light sources, to enter the light guide plate
from the rear end face, it is possible to make the light guide plate
appear to emit light uniformly in the front view of the lamp.

[0021] In this case, since the longitudinal width of the reflective
element, which is positioned on the further front side of the respective
reflective elements, is set to the larger value, it is possible to obtain
the following functional effect.

[0022] Light guided in the light guide plate gradually decreases toward
the front side. Accordingly, by setting the longitudinal width of the
reflective element, which is positioned on the further front side, to a
larger value, it is possible to make the intensity of light, which is
internally reflected by the respective reflective elements and emitted
from the second surface to the front side of the lamp, more uniform
between the respective reflective elements. Therefore, it is possible to
make the light guide plate appear to emit light uniformly in the front
view of the lamp.

[0023] In this case, a level difference between the front or rear end
edges of the reflective elements, which are positioned on the front side,
is large. However, since the light guide plate gradually becomes thinner
toward the front side, it is possible to prevent a level difference
between the respective reflective elements from becoming excessively
large.

[0024] If the light guide plate is curved to the second surface toward an
end portion in a direction orthogonal to the longitudinal direction in
the above-mentioned structure, a direction in which the light guide plate
is curved in the longitudinal direction is opposite to a direction in
which the light guide plate is curved in a direction orthogonal to the
longitudinal direction. Accordingly, it is possible to make the design of
the lamp have originality or to increase the degree of freedom in the
layout of the lamp. For example, when the light guide plate is disposed
so as to surround another lamp unit at the rear end area of the light
guide plate, it is possible to obtain a design where the light guide
plate is curved and widened forward toward the outer periphery from the
periphery of the lamp unit. A "direction orthogonal to the longitudinal
direction" in this case may be a width direction, a vertical direction,
or an inclined direction. Further, "curved to the second surface toward
an end portion in a direction orthogonal to the longitudinal direction"
means that the first surface is convex and the second surface side is
curved to be convex in a direction orthogonal to the longitudinal
direction.

[0025] Other aspects, features and advantages will be apparent from the
following detailed description, the accompanying drawings, and the
claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The above and other aspects of the present invention will become
more apparent from the following description of exemplary embodiments,
taken in conjunction with the accompanying drawings of which:

[0027]FIG. 1 is a side cross-sectional view of a vehicle lamp according
to an embodiment.

[0032]FIG. 6 is a view, which is the same as FIG. 3, showing a vehicle
lamp according to a modification of the embodiment.

DETAILED DESCRIPTION

[0033] An example of an embodiment of the invention is described below
with reference to the drawings.

[0034]FIG. 1 is a side cross-sectional view of a vehicle lamp 10.
Further, FIG. 2 is a view seen in the direction of arrow II of FIG. 1,
and FIG. 3 is a view seen in the direction of arrow III of FIG. 1.

[0035] As shown in these drawings, the vehicle lamp 10 is a daytime
operating lamp that is provided at the left front end portion of a
vehicle and is assembled in a lamp chamber, which is formed by a lamp
body 12 and a transparent and translucent cover 14 mounted on the front
end opening of the lamp body 12, together with a headlamp unit 50.

[0036] The vehicle lamp 10 includes a plurality of light-emitting diodes
22 and a light guide plate 24.

[0037] As shown in FIG. 1, the light guide plate 24 is adapted to emit
light to the front side of the lamp from its upper surface 24c by
internally reflecting light, which is emitted from the respective
light-emitting diodes 22, by a plurality of reflective elements 24s
formed on a lower surface 24b thereof after causing the light to enter
the light guide plate from a rear end face 24a thereof.

[0038] A rear area 24A of the light guide plate 24 from the rear end face
24a to a predetermined front range is in the shape of a flat plate so as
to extend along a horizontal plane, but a main area 24B formed on the
front side of the rear area 24A is curved to the lower surface 24b and
gradually becomes thinner toward the front side. Further, a front end
area 24C of the light guide plate 24 is even more curved to the lower
surface 24b toward the front side, and the thickness of the front end
area 24C is slightly larger than that of the front end portion of the
main area 24B.

[0039] As shown in FIG. 3, the light guide plate 24 is curved rearward
toward its left end portion (the right end portion in FIG. 3, similarly
hereinafter) in a width direction of a vehicle. In accordance with this
feature, the rear end face 24a of the light guide plate 24 is displaced
in the shape of a staircase at every position corresponding to the
respective light-emitting diodes 22. Further, as shown in FIG. 2, the
light guide plate 24 is curved to the upper surface 24c toward the left
end portion thereof. Furthermore, the light guide plate 24 is fixed to
the lamp body 12 at the lower end position and both left and right end
positions of the front end area 24C.

[0040] The light-emitting diodes 22 are disposed near the rear end face
24a of the light guide plate 24 so as to face the front side. Further,
the light-emitting diodes 22 are disposed at substantially regular
intervals in the width direction. In this case, the light-emitting diode
22, which is positioned on the further left side of the plurality of
light-emitting diodes 22, is displaced further rearward in accordance
with the rear end face 24a of the light guide plate 24 that is formed in
the shape of a staircase.

[0041] The light-emitting diodes 22 are fixed to upper end portions of the
front surfaces of vertically long substrates 26, respectively. Further,
the substrates 26 are fixed to the front surfaces of heat sinks 28 that
extend in a vertical direction of the vehicle so as to have a
substantially π-shaped cross-section, respectively. Furthermore, the
respective heat sinks 28 are fixed to a common light source supporting
member 30. Moreover, the light source supporting member 30 is fixed to
the lamp body 12.

[0042] A reflective panel 32, which is formed to extend substantially
along the shape of the light guide plate 24, is disposed near the lower
portion of the light guide plate 24. Since mirror surface treatment is
performed on an upper surface 32a of the reflective panel 32, the
reflective panel 32 is adapted to reflect the light that slightly leaks
downward from the light guide plate 24.

[0043] The rear area of the reflective panel 32 comes into close contact
with the rear area 24A of the light guide plate 24, and the other area of
the reflective panel is separated from the light guide plate 24. In this
case, the reflective panel 32 is formed so that a gap between the light
guide plate 24 and the reflective panel 32 gradually increases from the
rear end position of the main area 24B of the light guide plate 24 toward
the front end position of the main area. Further, the rear end face of
the reflective panel 32 comes into contact with the substrates 26, and
the lower surface of the front end portion of the reflective panel comes
into contact with the lamp body 12.

[0044] The headlamp unit 50 is positioned near the upper portion of the
rear area 24A of the light guide plate 24.

[0045] The headlamp unit 50 includes a light source bulb 52 and a
reflector 54 that reflects the light emitted from the light source bulb
52 to the front side. Further, the headlamp unit 50 is supported on the
lamp body 12 by an aiming mechanism (not shown).

[0046] The light guide plate 24 detours around the headlamp unit 50 from
the lower side of the headlamp unit to the left side of the headlamp
unit.

[0047] An extension member 60, which is formed in an annular shape so as
to cover the front end opening of the reflector 54, is disposed near the
front portion of the headlamp unit 50.

[0048] The extension member 60 is disposed so that the lower area of the
extension member 60 is positioned at a boundary portion between the rear
area 24A and the main area 24B of the light guide plate 24, and the outer
peripheral edge 60a of the lower end of the extension member 60 extends
to a position that is slightly lower than the upper surface of the rear
area 24A of the light guide plate 24.

[0049]FIG. 4 is a view showing in greater detail the light guide plate
24, which is extracted from the vehicle lamp 10 shown in FIG. 1, and
optical paths of light, which is emitted from the light-emitting diodes
22. FIG. 5 is a detailed view of a V portion of FIG. 4.

[0050] In this case, FIG. 4 shows an optical path of light that is emitted
from the light emission center O of the light-emitting diode 22 and
enters the light guide plate 24 from the rear end face 24a.

[0051] As shown in FIG. 4, the reflective elements 24s are formed on the
main area 24B and the front end area 24C of the light guide plate 24.

[0052] The reflective elements 24s extend in the width direction and are
disposed at substantially regular intervals in a longitudinal direction
of the vehicle. In this case, the longitudinal width of the reflective
element 24s, which is positioned on the further front side, of the
respective reflective elements 24s is set to a larger value.

[0053] That is, as shown in FIG. 5, the respective reflective elements 24s
the main area 24B are formed so that the pitch P of the reflective
elements 24s in the longitudinal direction is substantially constant and
the longitudinal width d of each of the reflective elements 24s gradually
increases toward the front end position from the rear end position of the
main area 24B.

[0054] Accordingly, as for light that enters the light guide plate 24 from
the rear end face 24a of the light guide plate 24 and is guided to the
front side while the total reflection of the light is sequentially
repeated by the lower surface 24b and the upper surface 24c, the
probability that the light reaches the reflective element 24s decreases
at the position near the rear end position of the main area 24B and the
probability that the light reaches the reflective element 24s increases
as the light approaches the front end position of the main area 24B. As a
result, the light is guided smoothly to the front end portion of the
light guide plate 24.

[0055] As shown in FIG. 3, the reflective elements 24s are formed in the
shape of a staircase at every position corresponding to the respective
light-emitting diodes 22, as band-like areas 24Z extending in the
longitudinal direction.

[0056] Functional effects of this embodiment are described below.

[0057] The vehicle lamp 10 according to this embodiment is adapted to emit
light to the front side of the lamp from the upper surface 24c (that is,
a second surface facing the lower surface 24b) by internally reflecting
light, which is emitted from the respective light-emitting diodes 22
(i.e., light sources), by the reflective elements 24s on the lower
surface 24b (i.e., a first surface) after causing the light to enter the
light guide plate 24 from the rear end face 24a. However, since the light
guide plate 24 is curved to the lower surface 24b and gradually becomes
thinner toward the front side and the reflective elements 24s are
disposed at a predetermined interval in the longitudinal direction and
extend in the width direction (i.e., a direction crossing the
longitudinal direction), it is possible to obtain the following
functional effect.

[0058] Light, which enters the light guide plate 24 from the rear end face
24a of the light guide plate 24, is guided to the front side while the
total reflection of the light is repeated sequentially by the lower
surface 24b and the upper surface 24c, but the light guide plate 24 is
curved forward to the lower surface 24b. Accordingly, at a position ahead
of the rear end face 24a to some extent, a portion of the light, which is
internally reflected by the reflective elements 24s of the lower surface
24b, reaches the upper surface 24c at an incidence angle smaller than a
critical angle and is emitted from the upper surface 24c to the front
side of the lamp. Further, a portion of the light, which continues to be
further guided, is reflected internally at a position further ahead of
the position by the reflective elements 24s of the lower surface 24b,
reaches the upper surface 24c at an incidence angle smaller than a
critical angle, and is emitted from the upper surface 24c to the front
side of the lamp.

[0059] In this case, since the light guide plate 24 gradually becomes
thinner toward the front side, it is possible to obtain the following
functional effect.

[0060] If the thickness of the light guide plate 24, which is curved to
the lower surface 24b toward the front side, is constant, it is necessary
to make larger a level difference between the rear end edges of the
reflective elements 24s, which are positioned on the further front side,
of the respective reflective elements 24sto cause the light, which is
internally reflected by the reflective elements 24s of the lower surface
24b, to reach the upper surface 24c at an incidence angle smaller than a
critical angle. However, the light, which is guided to the front end
portion of the light guide plate 24, decreases in this case. In that
regard, since the light guide plate 24 of this embodiment gradually
becomes thinner toward the front side, it is possible to prevent a level
difference between the respective reflective elements 24s from becoming
excessively large and to guide light easily to the front end portion of
the light guide plate 24. Accordingly, it is possible to cause the light
guide plate 24 to appear to emit light uniformly in the front view of the
lamp.

[0061] According to this embodiment, even when the guide plate 24 of the
vehicle lamp 10 including the light guide plate 24 is adapted to cause
light, which is emitted from the respective light-emitting diodes 22, to
enter the light guide plate from the rear end face 24a, it is possible to
cause the light guide plate 24 to appear to emit light uniformly in the
front view of the lamp.

[0062] In this case, since the longitudinal width d of the reflective
element 24s, which is positioned on the further front side, of the
respective reflective elements 24s is set to a larger value in this
embodiment, it is possible to obtain the following functional effect.

[0063] The light guided in the light guide plate 24 gradually decreases
toward the front side. Accordingly, by setting the longitudinal width d
of the reflective element 24s, which is positioned on the further front
side, to a larger value as in this embodiment, it is possible to make
more uniform the intensity of light, which is internally reflected by the
respective reflective elements 24s and emitted from the upper surface 24c
to the front side of the lamp, between the respective reflective elements
24s. Therefore, it is possible to cause the light guide plate 24 to
appear to emit light uniformly in the front view of the lamp.

[0064] Meanwhile, in this case, a level difference between the rear end
edges of the reflective elements 24s, which are positioned on the front
side, is large. However, since the light guide plate 24 gradually becomes
thinner toward the front side, it is possible to prevent a level
difference between the respective reflective elements 24s from becoming
excessively large.

[0065] In addition, since the pitch P of the reflective elements 24s,
which are formed on the main area 24B, in the longitudinal direction is
set to a substantially constant value in this embodiment, it is possible
to obtain the following functional effect.

[0066] As for light that enters the light guide plate 24 from the rear end
face 24a of the light guide plate 24 and is guided to the front side
while the total reflection of the light is repeated sequentially by the
lower surface 24b and the upper surface 24c, the probability that the
light reaches the reflective element 24s decreases since a value t (=P-d)
is large at the position near the rear end position of the main area 24B
and the probability that the light reaches the reflective element 24s
increases since a value t gradually decreases as the light approaches the
front end position of the main area 24B. Accordingly, it is possible to
guide the light to the front end portion of the light guide plate 24 more
smoothly.

[0067] Further, since the light guide plate 24 is curved to the upper
surface 24c toward the left end portion in the width direction in this
embodiment, a direction in which the light guide plate 24 is curved in
the longitudinal direction is opposite to a direction in which the light
guide plate 24 is curved in the width direction. Accordingly, it is
possible to make the design of the lamp have originality or to increase
the degree of freedom in the layout of the lamp. That is, in this
embodiment, the light guide plate 24 surrounds the headlamp unit 50 at
the rear area 24A. However, in this case, it is possible to obtain a
design where the light guide plate 24 is curved and widened forward
toward the outer periphery from the periphery of the headlamp unit 50.

[0068] In the foregoing example, the value t (=P-d) is set to decrease
gradually toward the front end position after the pitch P of the
respective reflective elements 24s in the longitudinal direction is set
to a substantially constant value, in order to make the longitudinal
width d of each of the reflective elements 24s gradually increase toward
the front end position from the rear end position of the main area 24B.
However, instead of this, the pitch P of the respective reflective
elements 24s in the longitudinal direction may be set to gradually
increase toward the front end position after the value t (=P-d) is set to
a substantially constant value.

[0069] Moreover, in the foregoing example, the respective reflective
elements 24s extend in the width direction. However, the respective
reflective elements may extend in a direction such that the respective
reflective elements are inclined in the longitudinal direction with
respect to the width direction (for example, a direction parallel to the
front end edge of the light guide plate 24).

[0070] An example in which the vehicle lamp 10 is a daytime operating lamp
provided at the left front end portion of a vehicle has been described in
the foregoing example. However, even in a case where the vehicle lamp 10
is a daytime operating lamp provided at the right front end portion of a
vehicle, a case where the vehicle lamp 10 is a lamp other than a daytime
operating lamp, and a case where the vehicle lamp 10 is a lamp provided
at the rear end portion of a vehicle, it is possible to obtain the same
functional effects as described above by employing the same structure as
the structure of the foregoing example.

[0071] A modification of the above-mentioned embodiment is described next.

[0072]FIG. 6 is a view, which is the same as FIG. 3, showing a vehicle
lamp 110 according to a modification of the forgoing example.

[0073] As shown in FIG. 6, the basic structure of the vehicle lamp 110
according to this modification is the same as that in the foregoing
example, but the shape of a rear end face 124a of a light guide plate 124
of the vehicle lamp 110 is partially different from that in the case of
the light guide plate 24 of the previous example.

[0074] In particular, lens portions 124d, which cause light emitted from
the respective light-emitting diodes 22 to enter the light guide plate
124 in the form of light substantially parallel to a vertical plane, are
formed at the positions, which correspond to the respective
light-emitting diodes 22, on the rear end face 124a of the light guide
plate 124 of this implementation.

[0075] It is possible to make the light, which is emitted from the
respective light-emitting diodes 22, efficiently enter band-like areas
124Z, which are positioned in front of the respective light-emitting
diodes, by employing the structure of this implementation. Accordingly,
it is possible to make the respective reflective elements 124s of the
light guide plate 124 appear to emit light more brightly in the front
view of the lamp.

[0076] The numerical values, which are described in the foregoing examples
as dimensions, are merely illustrative; the dimensions may be
appropriately set to different values in other implementations.